1. Field of the Invention
This invention relates generally to the field of in circuit emulation (ICE). More specifically, the present invention relates to power sources used to activate a device under test (DUT) on a test pod used in an ICE system. An embodiment of the present invention relates to protection of a DUT on a test pod from the simultaneous application of more than one power source.
2. Related Art
In circuit emulation (ICE) has been used by software and hardware developers for a number of years as a development tool to emulate the operation of complex circuit building blocks. Such ICE is most commonly used currently to analyze and debug the behavior of complex devices such as microcontrollers and microprocessors that have internal structures that are far too complex to readily model using computer simulation software alone.
An exemplary conventional ICE arrangement used to model, analyze and debug the operation of a circuit such as a microcontroller consists of a host computer (e.g., a personal computer) connected to an ICE which is further connected to a pod providing coupling to a circuit or microcontroller to be tested.
Existing ICE systems have a number of disadvantages and limitations. Firstly, the power required to operate a DUT is typically supplied by the ICE power grid. In general, the ICE power grid may not be capable of supplying power at various voltage levels and at power ratings required for different circuit designs. In order to overcome such disadvantages, the pod on which a DUT is mounted may have provisions for connection to external power sources.
However, the ability to apply external power to the pod offers a second disadvantage. That is, the possibility of damage to the DUT as well as the ICE system may occur if external power is erroneously or inadvertently applied simultaneously with power from the ICE power grid.
Furthermore, existing in circuit emulation systems do not always provide the ability to determine if power is being correctly applied to a DUT.